Use <> instead of () for casts & typeof

This makes it clearer that they aren't functions, and it eliminates
syntactic ambiguity with closure expressions.

blueprintcompiler/language/expression.py

@@ -159,7 +159,17 @@ class LookupOp(InfixExpr):
 
 
 class CastExpr(InfixExpr):
-    grammar = ["as", "(", TypeName, ")"]
+    grammar = [
+        "as",
+        AnyOf(
+            ["<", TypeName, Match(">").expected()],
+            [
+                UseExact("lparen", "("),
+                TypeName,
+                UseExact("rparen", ")").expected("')'"),
+            ],
+        ),
+    ]
 
     @context(ValueTypeCtx)
     def value_type(self):
@@ -183,6 +193,19 @@ class CastExpr(InfixExpr):
                 f"Invalid cast. No instance of {self.lhs.type.full_name} can be an instance of {self.type.full_name}."
             )
 
+    @validate("lparen", "rparen")
+    def upgrade_to_angle_brackets(self):
+        if self.tokens["lparen"]:
+            raise UpgradeWarning(
+                "Use angle bracket syntax introduced in blueprint 0.8.0",
+                actions=[
+                    CodeAction(
+                        "Use <> instead of ()",
+                        f"<{self.children[TypeName][0].as_string}>",
+                    )
+                ],
+            )
+
 
 class ClosureArg(AstNode):
     grammar = ExprChain

blueprintcompiler/language/types.py

@@ -89,6 +89,15 @@ class TypeName(AstNode):
         if self.gir_type:
             return self.gir_type.doc
 
+    @property
+    def as_string(self) -> str:
+        if self.tokens["extern"]:
+            return "$" + self.tokens["class_name"]
+        elif self.tokens["namespace"]:
+            return f"{self.tokens['namespace']}.{self.tokens['class_name']}"
+        else:
+            return self.tokens["class_name"]
+
 
 class ClassName(TypeName):
     @validate("namespace", "class_name")

blueprintcompiler/language/values.py

@@ -74,9 +74,18 @@ class Translated(AstNode):
 class TypeLiteral(AstNode):
     grammar = [
         "typeof",
-        "(",
+        AnyOf(
+            [
+                "<",
                 to_parse_node(TypeName).expected("type name"),
-        Match(")").expected(),
+                Match(">").expected(),
+            ],
+            [
+                UseExact("lparen", "("),
+                to_parse_node(TypeName).expected("type name"),
+                UseExact("rparen", ")").expected("')'"),
+            ],
+        ),
     ]
 
     @property
@@ -93,6 +102,19 @@ class TypeLiteral(AstNode):
         if expected_type is not None and not isinstance(expected_type, gir.TypeType):
             raise CompileError(f"Cannot convert GType to {expected_type.full_name}")
 
+    @validate("lparen", "rparen")
+    def upgrade_to_angle_brackets(self):
+        if self.tokens["lparen"]:
+            raise UpgradeWarning(
+                "Use angle bracket syntax introduced in blueprint 0.8.0",
+                actions=[
+                    CodeAction(
+                        "Use <> instead of ()",
+                        f"<{self.children[TypeName][0].as_string}>",
+                    )
+                ],
+            )
+
 
 class QuotedLiteral(AstNode):
     grammar = UseQuoted("value")

tests/sample_errors/warn_old_extern.err

@@ -1,3 +1,4 @@
 3,1,8,Use the '$' extern syntax introduced in blueprint 0.8.0
+4,15,15,Use angle bracket syntax introduced in blueprint 0.8.0
 4,16,13,Use the '$' extern syntax introduced in blueprint 0.8.0
 5,14,7,Use the '$' extern syntax introduced in blueprint 0.8.0

tests/samples/expr_closure.blp

@@ -1,5 +1,5 @@
 using Gtk 4.0;
 
 Label my-label {
-  label: bind ($my-closure(my-label.margin-bottom)) as (string);
+  label: bind ($my-closure(my-label.margin-bottom)) as <string>;
 }

tests/samples/expr_closure_args.blp

@@ -1,5 +1,5 @@
 using Gtk 4.0;
 
 Label {
-  label: bind $my-closure (true, 10, "Hello") as (string);
+  label: bind $my-closure (true, 10, "Hello") as <string>;
 }

tests/samples/expr_lookup.blp

@@ -5,5 +5,5 @@ Overlay {
 }
 
 Label {
-  label: bind (label.parent) as (Overlay).child as (Label).label;
+  label: bind (label.parent) as <Overlay>.child as <Label>.label;
 }

tests/samples/template_binding.blp

@@ -1,5 +1,5 @@
 using Gtk 4.0;
 
 template MyTemplate : Box {
-  prop1: bind MyTemplate.prop2 as ($MyObject).prop3;
+  prop1: bind MyTemplate.prop2 as <$MyObject>.prop3;
 }

tests/samples/template_binding_extern.blp

@@ -1,5 +1,5 @@
 using Gtk 4.0;
 
 template MyTemplate : $MyParentClass {
-  prop1: bind MyTemplate.prop2 as ($MyObject).prop3;
+  prop1: bind MyTemplate.prop2 as <$MyObject>.prop3;
 }

tests/samples/typeof.blp

@@ -3,9 +3,9 @@ using GObject 2.0;
 using Gio 2.0;
 
 Gio.ListStore {
-  item-type: typeof(GObject.Object);
+  item-type: typeof<GObject.Object>;
 }
 
 Gio.ListStore {
-  item-type: typeof($MyObject);
+  item-type: typeof<$MyObject>;
 }